65 ILCS 5/7-1-19

When the whole of a municipality is annexed to another municipality, and the annexed municipality has passed the annual appropriation ordinance, but not an ordinance levying a tax for the purpose of collecting a sufficient sum of money to defray the total amount of appropriations for all corporate purposes for that fiscal year, the annexing municipality may include the amount of the appropriations of the annexed municipality in the annual tax levy of the annexing municipality, the same as though the appropriations had been made by the annexing municipality. The fund derived from this part of the tax levy shall be used by the annexing municipality for the purpose for which the appropriations were made by the annexed municipality.